An American study finds that exposure to air pollution can increase the risk of obesity and insulin resistance, a precursor of type 2 diabetes. Air pollution has long been associated with the development of diabetes, but organisations such as the NHS and National Institutes of Health do not recognise pollution as a risk factor for diabetes. Researchers from Duke University observed that pregnant rats that breathed highly polluted air in Beijing experienced weight gain and cardio-respiratory and metabolic dysfunction. The pregnant rats used in the study were either exposed to polluted air or filtered air which removed most of the air pollution particles. After 19 days, the researchers observed that the lungs and livers of the rats exposed to air pollution were heavier and had increased tissue inflammation. Inflammation is thought to be responsible for the development of insulin resistance, which then triggers the development of type 2 diabetes. Compared to the rats breathing filtered air, these rats also had higher levels of insulin resistance; higher low-density lipoprotein (LDL) cholesterol; 46 per cent higher triglycerides; and 97 per cent higher total cholesterol. The pollution-exposed rats were significantly heavier at the end of pregnancy, and the offspring of these rats weighed more at eight weeks than the offspring of the other rats. The rats in both study groups were fed the same diet. The researchers highlighted that the adverse effects of air pollution were more pronounced at eight weeks than three weeks. They believe this suggests that long-term exposure is what generates the inflammation, insulin resistance and other metabolic changes that increase body weight and the risk of type 2 diabetes. Study author Junfeng Zhang, Duke University, said: “Since chronic inflammation is recognised as a factor contributing to obesity and since metabolic diseases such as diabetes and obesity are closely related, our findings provide clear evidence that chronic exposure to air pollution increases the risk for developing obesity. “If translated and verified in humans, these findings will support the urgent need to reduce air pollution, given the growing burden of obesity in today’s highly polluted world,” Zhang added. The study was published in the Journal of the Federation of American Societies for Experimental Biology.